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Huter P, Arenz S, Bock LV, Graf M, Frister JO, Heuer A, Peil L, Starosta AL, Wohlgemuth I, Peske F, Nováček J, Berninghausen O, Grubmüller H, Tenson T, Beckmann R, Rodnina MV, Vaiana AC, Wilson DN. Structural Basis for Polyproline-Mediated Ribosome Stalling and Rescue by the Translation Elongation Factor EF-P. Mol Cell 2017; 68:515-527.e6. [PMID: 29100052 DOI: 10.1016/j.molcel.2017.10.014] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Revised: 09/29/2017] [Accepted: 10/11/2017] [Indexed: 12/15/2022]
Abstract
Ribosomes synthesizing proteins containing consecutive proline residues become stalled and require rescue via the action of uniquely modified translation elongation factors, EF-P in bacteria, or archaeal/eukaryotic a/eIF5A. To date, no structures exist of EF-P or eIF5A in complex with translating ribosomes stalled at polyproline stretches, and thus structural insight into how EF-P/eIF5A rescue these arrested ribosomes has been lacking. Here we present cryo-EM structures of ribosomes stalled on proline stretches, without and with modified EF-P. The structures suggest that the favored conformation of the polyproline-containing nascent chain is incompatible with the peptide exit tunnel of the ribosome and leads to destabilization of the peptidyl-tRNA. Binding of EF-P stabilizes the P-site tRNA, particularly via interactions between its modification and the CCA end, thereby enforcing an alternative conformation of the polyproline-containing nascent chain, which allows a favorable substrate geometry for peptide bond formation.
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Affiliation(s)
- Paul Huter
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Stefan Arenz
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Lars V Bock
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Michael Graf
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Jan Ole Frister
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Andre Heuer
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Lauri Peil
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Agata L Starosta
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Ingo Wohlgemuth
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Frank Peske
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Jiří Nováček
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 62500 Brno, Czech Republic
| | - Otto Berninghausen
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Helmut Grubmüller
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Tanel Tenson
- University of Tartu, Institute of Technology, Nooruse 1, 50411 Tartu, Estonia
| | - Roland Beckmann
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Andrea C Vaiana
- Department of Theoretical and Computational Biophysics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen 37077, Germany
| | - Daniel N Wilson
- Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, Feodor-Lynenstr. 25, 81377 Munich, Germany; Institute for Biochemistry and Molecular Biology, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany.
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2
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Ramírez-Sarmiento CA, Noel JK, Valenzuela SL, Artsimovitch I. Interdomain Contacts Control Native State Switching of RfaH on a Dual-Funneled Landscape. PLoS Comput Biol 2015; 11:e1004379. [PMID: 26230837 PMCID: PMC4521827 DOI: 10.1371/journal.pcbi.1004379] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 06/03/2015] [Indexed: 11/22/2022] Open
Abstract
RfaH is a virulence factor from Escherichia coli whose C-terminal domain (CTD) undergoes a dramatic α-to-β conformational transformation. The CTD in its α-helical fold is stabilized by interactions with the N-terminal domain (NTD), masking an RNA polymerase binding site until a specific recruitment site is encountered. Domain dissociation is triggered upon binding to DNA, allowing the NTD to interact with RNA polymerase to facilitate transcription while the CTD refolds into the β-barrel conformation that interacts with the ribosome to activate translation. However, structural details of this transformation process in the context of the full protein remain to be elucidated. Here, we explore the mechanism of the α-to-β conformational transition of RfaH in the full-length protein using a dual-basin structure-based model. Our simulations capture several features described experimentally, such as the requirement of disruption of interdomain contacts to trigger the α-to-β transformation, confirms the roles of previously indicated residues E48 and R138, and suggests a new important role for F130, in the stability of the interdomain interaction. These native basins are connected through an intermediate state that builds up upon binding to the NTD and shares features from both folds, in agreement with previous in silico studies of the isolated CTD. We also examine the effect of RNA polymerase binding on the stabilization of the β fold. Our study shows that native-biased models are appropriate for interrogating the detailed mechanisms of structural rearrangements during the dramatic transformation process of RfaH. To carry out their biological functions, proteins must fold into defined three-dimensional structures. In most proteins, a single fold determined by the amino acid sequence, and sometimes influenced by environmental conditions, is believed to be suited for each protein’s dedicated task. However, some proteins challenge this broadly accepted paradigm, adopting different structures that can enable diverse roles or trigger pathological responses, such as prion diseases. Escherichia coli RfaH constitutes a dramatic example of this atypical behavior. RfaH C-terminal domain folds into either a helical bundle that binds to the N-terminal domain and inhibits unregulated recruitment to the transcription complex or, in the presence of a specific DNA target, into a stand-alone β-barrel structure that binds to the ribosome and couples transcription and translation of RfaH-dependent genes. To understand the mechanism of this structural rearrangement, we performed molecular dynamics using a model where the stabilizing interactions from both folds are integrated. Our results argue that this transformation requires destabilization of the domain interface, is favored by interactions between the N-terminal domain of RfaH and RNA polymerase, and proceeds via a bound intermediate state that connects both folds.
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Affiliation(s)
- César A. Ramírez-Sarmiento
- Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Ñuñoa, Santiago, Chile
- * E-mail: (CARS); (IA)
| | - Jeffrey K. Noel
- Center for Theoretical Biological Physics, Rice University, Houston, Texas, United States of America
| | - Sandro L. Valenzuela
- Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Ñuñoa, Santiago, Chile
| | - Irina Artsimovitch
- Department of Microbiology and The Center for RNA Biology, The Ohio State University, Columbus, Ohio, United States of America
- * E-mail: (CARS); (IA)
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3
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Yang X, Molimau S, Doherty GP, Johnston EB, Marles-Wright J, Rothnagel R, Hankamer B, Lewis RJ, Lewis PJ. The structure of bacterial RNA polymerase in complex with the essential transcription elongation factor NusA. EMBO Rep 2009; 10:997-1002. [PMID: 19680289 PMCID: PMC2750059 DOI: 10.1038/embor.2009.155] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Revised: 06/08/2009] [Accepted: 06/10/2009] [Indexed: 11/09/2022] Open
Abstract
There are three stages of transcribing DNA into RNA. These stages are initiation, elongation and termination, and they are well-understood biochemically. However, despite the plethora of structural information made available on RNA polymerase in the last decade, little is available for RNA polymerase in complex with transcription elongation factors. To understand the mechanisms of transcriptional regulation, we describe the first structure, to our knowledge, for a bacterial RNA polymerase in complex with an essential transcription elongation factor. The resulting structure formed between the RNA polymerase and NusA from Bacillus subtilis provides important insights into the transition from an initiation complex to an elongation complex, and how NusA is able to modulate transcription elongation and termination.
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Affiliation(s)
- Xiao Yang
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Seeseei Molimau
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Geoff P Doherty
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Elecia B Johnston
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
| | - Jon Marles-Wright
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne NE2 4HH, UK
| | - Rosalba Rothnagel
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Ben Hankamer
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Richard J Lewis
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne NE2 4HH, UK
| | - Peter J Lewis
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
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4
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Andersen CBF, Becker T, Blau M, Anand M, Halic M, Balar B, Mielke T, Boesen T, Pedersen JS, Spahn CMT, Kinzy TG, Andersen GR, Beckmann R. Structure of eEF3 and the mechanism of transfer RNA release from the E-site. Nature 2006; 443:663-8. [PMID: 16929303 DOI: 10.1038/nature05126] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Accepted: 08/03/2006] [Indexed: 11/08/2022]
Abstract
Elongation factor eEF3 is an ATPase that, in addition to the two canonical factors eEF1A and eEF2, serves an essential function in the translation cycle of fungi. eEF3 is required for the binding of the aminoacyl-tRNA-eEF1A-GTP ternary complex to the ribosomal A-site and has been suggested to facilitate the clearance of deacyl-tRNA from the E-site. Here we present the crystal structure of Saccharomyces cerevisiae eEF3, showing that it consists of an amino-terminal HEAT repeat domain, followed by a four-helix bundle and two ABC-type ATPase domains, with a chromodomain inserted in ABC2. Moreover, we present the cryo-electron microscopy structure of the ATP-bound form of eEF3 in complex with the post-translocational-state 80S ribosome from yeast. eEF3 uses an entirely new factor binding site near the ribosomal E-site, with the chromodomain likely to stabilize the ribosomal L1 stalk in an open conformation, thus allowing tRNA release.
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Affiliation(s)
- Christian B F Andersen
- Centre for Structural Biology, Department of Molecular Biology, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus, Denmark
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5
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Abstract
The ribosome is a complex macromolecular assembly capable of translating mRNA sequence into amino acid sequence. The adaptor molecule of translation is tRNA, but the delivery of aminoacyl-tRNAs--the primary substrate of the ribosome--relies on the formation of a ternary complex with elongation factor Tu (EF-Tu) and GTP. Likewise, elongation factor G (EF-G) is required to reset the elongation cycle through the translocation of tRNAs. Recent structures and biochemical data on ribosomes in complex with the ternary complex or EF-G have shed light on the mode of action of the elongation factors, and how this interplays with the state of tRNAs and the ribosome. A model emerges of the specific routes of conformational changes mediated by tRNA and the ribosome that trigger the GTPase activity of the elongation factors on the ribosome.
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Affiliation(s)
- Jakob Nilsson
- University of Aarhus, Department of Molecular Biology, Gustav Wieds Vej 10C, 8000 Arhus C, Denmark
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6
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Affiliation(s)
- M V Rodnina
- Institute of Molecular Biology, University of Witten/Herdecke, 58448 Witten, Germany
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7
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Agrawal RK, Penczek P, Grassucci RA, Frank J. Visualization of elongation factor G on the Escherichia coli 70S ribosome: the mechanism of translocation. Proc Natl Acad Sci U S A 1998; 95:6134-8. [PMID: 9600930 PMCID: PMC27598 DOI: 10.1073/pnas.95.11.6134] [Citation(s) in RCA: 275] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
During protein synthesis, elongation factor G (EF-G) binds to the ribosome and promotes the step of translocation, a process in which tRNA moves from the A to the P site of the ribosome and the mRNA is advanced by one codon. By using three-dimensional cryo-electron microscopy, we have visualized EF-G in a ribosome-EF-G-GDP-fusidic acid complex. Fitting the crystal structure of EF-G-GDP into the cryo density map reveals a large conformational change mainly associated with domain IV, the domain that mimics the shape of the anticodon arm of the tRNA in the structurally homologous ternary complex of Phe-tRNAPhe, EF-Tu, and a GTP analog. The tip portion of this domain is found in a position that overlaps the anticodon arm of the A-site tRNA, whose position in the ribosome is known from a study of the pretranslocational complex, implying that EF-G displaces the A-site tRNA to the P site by physical interaction with the anticodon arm.
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Affiliation(s)
- R K Agrawal
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201-0509, USA
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8
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Abstract
The cloning and sequencing of the gene coding for Trypanosoma cruzi elongation factor 1 alpha (TcEF-1 alpha) was performed by screening a T. cruzi genomic library with a probe obtained through the polymerase chain reaction (PCR) amplification of T. cruzi DNA using two oligonucleotides deduced from the sequence of T. brucei EF-1 alpha. Southern blot analysis of T. cruzi digested genomic DNA and Northern blot hybridized with the labeled probe revealed that one copy of TcEF-1 alpha exist in the genome of the parasite. Indirect immunofluorescence technique using anti-EF-1 alpha antibodies and epimastigotes harvested after different days of in vitro culture showed that EF-1 alpha is localised in the cytoplasm of the parasites from the exponential growth phase. Surprisingly, during the stationary phase (ageing parasites), EF-1 alpha was found in the nucleus. Furthermore, treatment of parasites with the antibiotic drug geneticin (G418) which induces the death of epimastigotes by apoptosis showed selective localization of EF-1 alpha in the nucleus of dying parasites. This observation supports the notion already reported in the case of mammalian cells that EF-1 alpha could participate in the transcription processes and possibly in the case of T. cruzi, in the expression regulation of genes involved in the control of cell death. The possible transfection and genomic manipulation of T. cruzi may provide a model to study the role of TcEF-1 alpha in this phenomenon.
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Affiliation(s)
- O Billaut-Mulot
- Laboratoire de recherche sur les Trypanosomatidae, U415, Institut Pasteur, Lille, France
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9
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Abstract
The NusG-like protein from Thermotoga maritima was expressed in Escherichia coli and purified to homogeneity. Purified T. maritima NusG exhibited a generalized, non-sequence-specific and highly cooperative DNA and RNA binding activity. The complexes formed between nucleic acid and T. maritima NusG were unable to penetrate a polyacrylamide or agarose gel. The affinity of the protein for DNA was highest in buffers containing about 50 mM salt. The DNA-protein complexes could not be stained with ethidium bromide, were resistant to digestion by TaqI endonuclease, were able to be transcribed in vitro by T. maritima RNA polymerase, and contained a minimum of about 30 to 40 monomers of NusG per kb of duplex DNA. The protein had comparable affinities for duplex DNA and RNA but a lower affinity for single-stranded DNA. Electron microscopy showed that the DNA in the complex is condensed within a large structure that resembles the complex between DNA and histone-like protein Hcl from Chlamydia trachomatis. Neither the wild-type T. maritima nusG gene nor a deletion derivative more similar to the E. coli gene was able to substitute for the essential E. coli nusG. Two variants of the NusG protein were constructed, expressed, and purified: one contains only the entire 171-amino-acid insertion that is unique to T. maritima NusG, and the other has only the sequences present in NusG homologs from E. coli and other eubacteria. Both variants exhibited similar DNA and RNA binding behavior, although their apparent affinities were 5- to 10-fold lower than that of the wild-type T. maritima NusG.
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Affiliation(s)
- D Liao
- Program in Evolutionary Biology, Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
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10
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Liljas A, AEvarsson A, al-Karadaghi S, Garber M, Zheltonosova J, Brazhnikov E. Crystallographic studies of elongation factor G. Biochem Cell Biol 1995; 73:1209-16. [PMID: 8722038 DOI: 10.1139/o95-130] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The elongation factors G (EF-G) and Tu (EF-Tu) go through a number of conformation states in their functional cycles. Since they both are GTPases, have similar G domains and domains II, and have similar interactions with the nucleotides, then GTP hydrolysis must occur in similar ways. The crystal structures of two conformational states are known for EF-G and three are known for EF-Tu. The conformations of EF-G.GDP and EF-Tu.GTP are closely related. EF-Tu goes through a large conformational change upon GTP cleavage. This conformational change is to a large extent due to an altered interaction between the G domain and domains II and III. A number of kirromycin-resistant mutations are situated at the interface between domains I and III. The interface between the G domain and domain V in EF-G corresponds with this dynamic interface in EF-Tu. The contact area in EF-G is small and dominated by interactions between charged amino acids, which are part of a system that is observed to undergo conformational changes. Furthermore, a number of fusidic acid resistant mutants have been identified in this area. All of this evidence makes it likely that EF-G undergoes a large conformational change in its functional cycle. If the structures and conformational states of the elongation factors are related to a scheme in which the ribosome oscillates between two conformations, the pretranslocational and posttranslocational states, a model is arrived at in which EF-Tu drives the reaction in one direction and EF-G in the opposite. This may lead to the consequence that the GTP state of one factor is similar to the GDP state of the other. At the GTP hydrolysis state, the structures of the factors will be close to superimposable.
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Affiliation(s)
- A Liljas
- Chemical Center, University of Lund, Sweden
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Billaut-Mulot O, Schöneck R, Fernandez-Gomez R, Taibi A, Capron A, Pommier V, Plumas-Marty B, Loyens M, Ouaissi A. Molecular and immunological characterization of a Trypanosoma cruzi protein homologous to mammalian elongation factor 1 gamma. Biol Cell 1994; 82:39-44. [PMID: 7735118 DOI: 10.1016/0248-4900(94)90064-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In previous studies, we reported the characterization of three Trypanosoma cruzi proteins with molecular masses of 45, 30 and 25 kDa eluted from a glutathione agarose column (these proteins were named TcGBP). Using antibodies against TcGBP native proteins we could isolate from a lambda ZAPII epimastigote cDNA library cDNA clones encoding the 30 and 25 kDa proteins. Comparison of the two sequences with amino acid sequences in several data banks revealed that both protein sequences were highly homologous to human and Artemia salina elongation factor 1 beta. Thus, the proteins were named TcEF-1 beta 25 and TcEF-1 beta 30. In the present study we used a double immunoscreening strategy that allowed us to isolate a cDNA clone corresponding to the 45 kDa protein. The protein sequence revealed 31% identity and 61% homology with human and Artemia salina EF1 gamma and therefore was named TcEF-1 gamma. Moreover, three putative phosphorylation sites at position 51 (CSPC), at position 90 (RTPL) and at position 265 (PSPF) were found in the TcEF-1 gamma sequence. These sites are compatible with the notion that TcEF-1 gamma could be the target of phosphorylation by protein kinase(s). Random primed cDNA hybridized with a single 1.4 kb mRNA found in epimastigote, trypomastigote and amastigote forms. In addition, Southern blot analysis of genomic DNA suggested that the protein is encoded by a single gene. The TcEF-1 gamma cDNA was subcloned into the pGEX-4T-3 vector for expression in Escherichia coli.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- O Billaut-Mulot
- Laboratoire de Recherche sur les Trypanosomatidae, INSERM U 415, Institut Pasteur, Lille, France
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12
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Pollard TD, Bhandari D, Maupin P, Wachsstock D, Weeds AG, Zot HG. Direct visualization by electron microscopy of the weakly bound intermediates in the actomyosin adenosine triphosphatase cycle. Biophys J 1993; 64:454-71. [PMID: 8457671 PMCID: PMC1262348 DOI: 10.1016/s0006-3495(93)81387-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We used a novel stopped-flow/rapid-freezing machine to prepare the transient intermediates in the actin-myosin adenosine triphosphatase (ATPase) cycle for direct observation by electron microscopy. We focused on the low affinity complexes of myosin-adenosine triphosphate (ATP) and myosin-adenosine diphosphate (ADP)-Pi with actin filaments since the transition from these states to the high affinity actin-myosin-ADP and actin-myosin states is postulated to generate the molecular motion that drives muscle contraction and other types of cellular movements. After rapid freezing and metal replication of mixtures of myosin subfragment-1, actin filaments, and ATP, the structure of the weakly bound intermediates is indistinguishable from nucleotide-free rigor complexes. In particular, the average angle of attachment of the myosin head to the actin filament is approximately 40 degrees in both cases. At all stages in the ATPase cycle, the configuration of most of the myosin heads bound to actin filaments is similar, and the part of the myosin head preserved in freeze-fracture replicas does not tilt by more than a few degrees during the transition from the low affinity to high affinity states. In contrast, myosin heads chemically cross-linked to actin filaments differ in their attachment angles from ordered at 40 degrees without ATP to nearly random in the presence of ATP when viewed by negative staining (Craig, R., L.E. Greene, and E. Eisenberg. 1985. Proc. Natl. Acad. Sci. USA. 82:3247-3251, and confirmed here), freezing in vitreous ice (Applegate, D., and P. Flicker. 1987. J. Biol. Chem. 262:6856-6863), and in replicas of rapidly frozen samples. This suggests that many of the cross-linked heads in these preparations are dissociated from but tethered to the actin filaments in the presence of ATP. These observations suggest that the molecular motion produced by myosin and actin takes place with the myosin head at a point some distance from the actin binding site or does not involve a large change in the shape of the myosin head.
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Affiliation(s)
- T D Pollard
- Department of Cell Biology and Anatomy, Johns Hopkins Medical School, Baltimore, Maryland 21205
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13
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Owen CH, DeRosier DJ, Condeelis J. Actin crosslinking protein EF-1a of Dictyostelium discoideum has a unique bonding rule that allows square-packed bundles. J Struct Biol 1992; 109:248-54. [PMID: 1296758 DOI: 10.1016/1047-8477(92)90037-b] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The elongation factor 1a (EF-1a) of Dictyostelium discoideum is an actin crosslinking protein that gives rise to a unique kind of actin bundle. Purified actin and EF-1a were allowed to form bundles and then were characterized by electron microscopy, computed diffraction analysis, and modeling. In these bundles crosslinked actin filaments are rotated by 90 degrees relative to each other, whereas other known crosslinking proteins require filaments to be unrotated. Bundles of actin EF-1a would tend to exclude other actin bundling proteins. EF-1a can thus regulate the state of the actin cytoskeleton as well as regulate protein synthesis.
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Affiliation(s)
- C H Owen
- Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254-9110
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14
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Bec G, Kerjan P, Zha XD, Waller JP. Valyl-tRNA synthetase from rabbit liver. I. Purification as a heterotypic complex in association with elongation factor 1. J Biol Chem 1989; 264:21131-7. [PMID: 2556394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Valyl-tRNA synthetase occurs as a high molecular mass entity of approximately equal to 700 kDa in the crude extract from rabbit liver. The enzyme was purified as a heterotypic complex comprising four polypeptides of 140, 50, 35, and 27 kDa in the molar proportions of 1:2:1:1, respectively, as determined by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Co-purification of these components at each step of the purification supports the conclusion that they are physically associated within the same complex. In addition to valyl-tRNA synthetase activity, which was assigned to the 140-kDa component, the purified complex exhibits a potent Elongation Factor 1 activity, determined by its ability to sustain poly(U)-dependent polyphenylalanine synthesis in the presence of Elongation Factor 2. Our results are essentially in agreement with those from a recent report (Motorin, Y., Wolfson, A., Orlovsky, A., and Gladilin, K. (1988) FEBS Lett. 238, 262-264), according to which the polypeptides other than that assigned to valyl-tRNA synthetase correspond to the subunits of Elongation Factor 1H.
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Affiliation(s)
- G Bec
- Laboratoire d'Enzymologie, Centre National de la Recherche Scientifique, Gif-sur-Yvette, France
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